Does the Lack of Coupling in SST-Forced Atmosphere-Only Models Limit Their Usefulness for Climate Change Studies?

Atmospheric general circulation models (AGCMs) are often considered inadequate for studying natural climate variability because of their lack of coupling with an underlying ocean. This lack of two-way air–sea coupling results in an inconsistency in surface energetics. This study aims to determine whether the lack of two-way air–sea coupling also undermines an AGCM’s ability to simulate anthropogenic climate change. A comparison between coupled and atmospheric GCM simulations shows that anthropogenic climate change can be well reproduced by an AGCM and that errors due to the lack of two-way coupling are primarily limited to internal variability. Simulations using a stochastic linear model are shown to further support this conclusion. These results suggest a greater utility for AGCMs as computationally efficient tools for understanding and downscaling coupled model simulations of anthropogenic climate change.